Invention Field
The present invention relates to marine jet propulsion systems, and in particular, to an enclosed shaft system for tunnel jet drive marine propulsion systems, for providing an improved lubrication and coolant system over current designs.
The preferred embodiment of the present invention contemplates the utilization of an enclosed shaft system wherein the drive impeller drives a portion of the water passing through the tunnel drive through a water intake, which water is filtered and directed to a "T" fitting, wherein a portion of the water is directed to the engine for cooling, and the remaining water is directed to the base of the shaft housing, wherein the water passes through an shaft sleeve enveloping the shaft, the shaft sleeve terminating at an open end wherein the cutlass bearing and impeller is fitted. The water passing through the shaft sleeve both lubricates the cutlass bearings, as well as cooling same.
Besides improving the overall performance of the shaft system and decreasing maintenance, the present system has been found to allow for utilization in environments which might be considered to harsh for conventional jet tunnel drive marine propulsion systems, which traditionally have had open shafts, and which traditionally have relied upon the tunnel drive water flow, driven by the propeller, for lubricating and cooling the cutlass bearings.
Unlike the known prior art systems, the present invention allows for the filtration of the water utilized for cooling and lubricating the cutlass bearings and shaft. Thus, in environments such which might have high particulate, such as chopped vegetation or sand, performance which is unhindered by the particulate, unlike the prior art, which has an open circulation system through the cutlass bearings and the propeller, which could trap particulate, damaging the bearings and overheating same.
Lastly, the present system provides improved performance of tunnel jet drive systems, in that the drive shaft of the present invention is sheathed and thereby removed from the flow of the tunnel drive passgage. Accordingly, vegitation such as seaweed and grass are prevented from wrapping around the rotating driveshaft and fouling same, unlike the prior art.